Question Re: Recursive CDS data type in Technology Q&A

Recursive CDS data type

former_member748892 — Fri, 28 May 2021 12:36:05 GMT

Dear colleagues,

I'm trying to create a recursive data type using SAP CDS version 5.0.6. So far I experimented with the following:

type Node { value: String; children: many Node; }

This yields an error: 'Illegal circular reference'. Do you know how can this use case modelled in CDS?

Thanks,

Daniel

Re: Recursive CDS data type

gregorw — Fri, 28 May 2021 12:50:41 GMT

Have you tried to follow the example in:

schema.cds#L27

Re: Recursive CDS data type

former_member628556 — Fri, 28 May 2021 15:38:37 GMT

Recursive type are indeed not supported in CDS. Before we would invest in this direction, we would have to check whether they would be supported in consumers of CDS models.

In SQL, it would be fine in combination with MANY (like your example), because then it would be mapped to a CLOB... In OData and OData consumers...

In CDS, you have recursive data structures via Associations/compositions

entity Node {
  key id: UUID;
  value: String;
  children: Composition of Node;
}

Regards,
Christoph

Re: Recursive CDS data type

former_member748892 — Fri, 28 May 2021 17:09:47 GMT

It did the trick, thanks!